V. Senkovskyy, N. Khanduyeva, M. Stamm, A. Kiriy
Leibniz-Institut für Polymerforschung Dresden, Hohe Straße 6, 01069 Dresden, Germany
We describe a new method to grow conductive polymer brushes of regioregular head-to-tail poly(3-alkylthiophenes) (P3AT) via surface initiated polycondensation of 2-bromo-5-chloromagnesio-3-alkylthiophene. We developed a simple procedure for the preparation of the Ni(II) macroinitiator by the reaction of Ni(PPh3)4 with photo-cross-linked poly(-4-bromostyrene) films. Exposure of the initiator layer to the monomer solution leads to selective polymerization of the monomer predominantly from the surface and not in the bulk solution, resulting into conductive polymer brushes in a very economical way. In contrast to the P3AT films prepared by traditional solvent casting methods, our approach gives an access to mechanically robust conductive polymer films, stable against delamination. Having in mind high processability of PS-Br and its copolymers along with the possibility to apply various standard lithography methods (such as contact molding or photolithography) to PS-Br, we believe that our approach represents a new dimension in fabrications of all-plastic devices. Investigation of the polymerization mechanism reveals that the Ni(PPh3)4-mediated polycondensation involves, rare for the chemistry of conductive polymers chain growth mechanism. We believe that this fact together with the ability of Ni(PPh3)4 to react easily with various arylhalides forming the initiators, might open the way to earlier inaccessible polymer architectures comprising conjugated polymers.